FIG. 9 is a cross-sectional view schematically showing a conventional solar cell. In FIG. 9, an active layer of the solar cell 500 comprises an n type Si layer 51 and a p type Si layer 52. A p side electrode 53 comprising a linear pattern is disposed on the p type Si layer 52 and an n side electrode 54 is disposed on the rear surface of the n type Si layer 51.
As a method for forming an electrode of such a conventional solar cell, vapor deposition or sputtering, screen printing drawing-printing, or the like has been employed. In addition, an Ag paste has been employed as an electrode material of the conventional solar cell. Recently, a low temperature baking Ag paste whose baking temperature is only 150.degree.-180.degree. C. has come to be used. If a high temperature baking Ag paste whose baking temperature is 700.degree.-800.degree. C. is used for forming an electrode of an amorphous silicon solar cell or a microcrystalline silicon/crystalline silicon junction-type solar cell, the junction in an active layer of the solar cell is damaged during the baking process.
Meanwhile, in the above-described screen printing method, an Ag paste comprising Ag powder, glass frit, and an organic binder is printed on a substrate through a print mask comprising a stainless mesh on which an emulsion pattern is formed and then it is dried and baked to form an electrode pattern having a desired resistivity. However, the minimum width of the electrode formed by this method is 100-150 microns and an electrode narrower than that cannot be formed. If the electrode 53 on the light receiving surface of the solar cell 500 shown in FIG. 9 is formed by this screen printing method, the width of the electrode 53 exceeds 100 microns, thereby decreasing the effective power generating area 55 of the incident light surface. In addition, when the electrode pattern is changed, a new screen mask is needed, resulting in a poor production yield.
Meanwhile, FIG. 8 is a schematic diagram showing a method for applying a paste on a substrate using a drawing-printing apparatus disclosed in Japanese Patent Published Application No. 64-39078. In the drawing-printing method, a tank 10 is filled with paste 13 and kept warm by constant-temperature water 14 circulating around the tank 10. The constant-temperature water 14 is sent from a constant-temperature tank 15 by a pump 17. The paste 13 is compressed by a float 12, to which air pressure 11 is applied, and discharged through a nozzle 18, and a desired pattern is drawn on a substrate 16. This method solves the problems in the conventional screen printing method. However, when a linear pattern having a width below 100 microns is drawn by this method using the low temperature baking Ag paste and then it is baked at 150.degree.-180.degree. C. to form an electrode pattern of an amorphous silicon solar cell or a microcrystalline silicon/crystalline silicon junction type solar cell, the resistivity of the electrode pattern is higher than 5.times.10.sup.-5 .OMEGA..multidot.cm, so that current generated in the cell is not efficiently taken out, adversely affecting the characteristics of the solar cell.
Furthermore, since above-described screen printing method and drawing-printing method use a paste, a step of baking the paste is required after forming the pattern, and the baking step takes a lot of time. Therefore, the pattern is not formed with high efficiency. In addition, when a high temperature baking paste is used, there is a sudden change of temperature between the baking step and a cooling step after the baking, so that the substrate, on which the pattern is formed, is unfavorably deformed by the temperature change.